Compared to a single view X-ray machine or a multi-view X-ray machine, CT (Computed Tomography) technology plays an important role on various applications such as security, since CT technology can eliminate an effect of object overlap to a great extent. However, in the case of security, contraband (on which a human operator focuses) can be of various types, including not only guns and cutters made of metal, but also sharp products made of glass, ceramic and/or aluminum which are referred to as mixtures, as well as various exploding devices which are categorized as organic, containing a flammable and/or explosive liquid. Since there are so many categories of objects required to be imaged, any of the categories cannot get a most notable and most elaborate display effect, which affects user experience and affects the inspection ability of the human operator using a CT system to some extent.